JP2023039296A - Abnormality determination apparatus - Google Patents

Abstract

To provide a simply configured abnormality determination apparatus capable of determining abnormality of a plasma generation device disposed in an exhaust channel.SOLUTION: An abnormality determination apparatus determines abnormality of a plasma generation device 16 that is disposed in an exhaust channel of an internal combustion engine and purifies an exhaust gas by generating plasma by discharging when a voltage is applied to the device. The abnormality determination apparatus includes: a voltage raise part 34c for raising a voltage applied to the plasma generation device 16 to a voltage higher than a voltage for generating plasma to purify the exhaust gas when determining abnormality of the plasma generation device 16; an NOx concentration acquisition part 34d for acquiring an NOx concentration in an exhaust gas flowing downstream of the plasma generation device 16 in a state where the voltage applied to the plasma generation device 16 is raised; and an abnormality determination part 34e for determining that the plasma generation device 16 is abnormal in a case where the NOx concentration is equal to or less than a given threshold.SELECTED DRAWING: Figure 3

Description

The present invention relates to an abnormality determination device.

Conventionally, in an exhaust purification system configured by arranging a plasma generation device and a NOx selective reduction catalyst that reduces NOx using HC in the exhaust as a reducing agent in the exhaust passage, the detection value of the NOx concentration detection means and the NH ₃ concentration It is known to determine failure of the plasma generator when the NOx concentration in the exhaust gas is equal to or higher than a first concentration and the NH ₃ concentration in the exhaust gas is lower than a second concentration based on the detection value of the detection means (for example, , Patent Document 1).

JP 2013-142350 A

However, according to the technique described in Patent Document 1, it is necessary to detect both the NOx concentration and the NH ₃ concentration in the exhaust gas in order to determine the abnormality of the plasma generation device. For this reason, two sensors, the NOx sensor and the _NH3 sensor, are required, and the number of parts for determining abnormality of the plasma generator increases, resulting in an increase in manufacturing cost.

Further, according to the technique described in Patent Document 1, there is a problem that it is not possible to determine whether the plasma generating device or the catalyst is malfunctioning unless the concentrations of both NOx and _NH3 are detected. In other words, if only one of the NOx concentration and the NH ₃ concentration in the exhaust gas is used, there is a problem that it cannot be determined which of the plasma generator and the HC selective reduction catalyst is abnormal. Therefore, the technique described in Patent Literature 1 has room for improvement from the viewpoint of simplifying the configuration for detecting an abnormality in the plasma generation device.

In view of the above problems, an object of the present disclosure is to provide an abnormality determination device capable of determining abnormality of a plasma generation device provided in an exhaust passage with a simple configuration.

The gist of the present disclosure is as follows.
(1) An anomaly judgment device for judging an anomaly of a plasma generation device provided in an exhaust passage of an internal combustion engine that generates plasma by electric discharge to purify exhaust gas when a voltage is applied, ,
a voltage raising unit for raising the voltage applied to the plasma generation device to a voltage higher than the voltage for generating plasma for exhaust gas purification when performing abnormality determination of the plasma generation device;
a NOx concentration acquisition unit that acquires the NOx concentration in the exhaust gas flowing through the exhaust passage downstream of the plasma generation device in a state where the voltage applied to the plasma generation device is increased;
an abnormality determination unit that determines that an abnormality has occurred in the plasma generation device when the NOx concentration is equal to or lower than a predetermined threshold;
An abnormality determination device.

According to the present disclosure, there is provided an abnormality determination device capable of determining abnormality in a plasma generation device provided in an exhaust passage with a simple configuration.

1 is a schematic diagram showing the configuration of an internal combustion engine; FIG. It is a perspective view which shows the structure of a plasma generation apparatus. 4 is a schematic diagram showing functional blocks of a CPU of the electronic control unit; FIG. 4 is a flowchart showing processing performed by a CPU;

Hereinafter, embodiments will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to the same constituent elements.

FIG. 1 shows an overall view of an internal combustion engine. This internal combustion engine is mounted in a vehicle such as an automobile. Note that the internal combustion engine may be mounted in a hybrid vehicle having an internal combustion engine and a motor as drive sources. Referring to FIG. 1, 1 is an engine main body, 2 is a combustion chamber of each cylinder, 3 is a spark plug arranged in the combustion chamber 2 of each cylinder, and 4 is a fuel for supplying fuel, for example, gasoline to each cylinder. A fuel injection valve, 5 is a surge tank, 6 is an intake branch pipe, and 7 is an exhaust manifold. The surge tank 5 is connected through an intake duct 8 to the outlet of a compressor 9a of an exhaust turbocharger 9, and the inlet of the compressor 9a is connected through an intake air amount detector 10 to an air cleaner 11. A throttle valve 12 driven by an actuator 13 is arranged in the air intake duct 8 , and an intercooler 14 is arranged around the air intake duct 8 for cooling intake air flowing through the air intake duct 8 .

On the other hand, the exhaust manifold 7 is connected to the inlet of the exhaust turbine 9b of the exhaust turbocharger 9, and the outlet of the exhaust turbine 9b is connected to the plasma generator 16 via the exhaust pipe 15a. An outlet of the plasma generator 16 is connected through an exhaust pipe 15b to a catalytic converter 17 containing an exhaust purification catalyst 17a. An outlet of the catalytic converter 17 is open to the atmosphere through an exhaust pipe 15c. The exhaust purification catalyst 17a is composed of a three-way catalyst into which the exhaust gas that has passed through the plasma generator 16 flows. The exhaust manifold 7 and the surge tank 5 are connected to each other through an exhaust gas recirculation (hereinafter referred to as EGR) passage 18, in which an EGR control valve 19 is arranged. Each fuel injection valve 4 is connected to a fuel distribution pipe 20 , which is connected to a fuel tank 22 via a fuel pump 21 . As shown in FIG. 1, the surge tank 5 is provided with a pressure sensor 23 and a temperature sensor 24 for detecting the pressure and temperature in the surge tank 5, respectively. Further, in the exhaust pipe 15a, an air-fuel ratio sensor 25 for detecting the air-fuel ratio of the exhaust gas flowing into the plasma generator 16, and an HC concentration sensor 26 for detecting the HC concentration in the exhaust gas or the exhaust gas A CO concentration sensor 26 is arranged for detecting the CO concentration inside. A NOx concentration sensor 28 for detecting the NOx concentration of the exhaust gas discharged from the plasma generator 16 and flowing into the catalytic converter 17 is arranged in the exhaust pipe 15b. Further, a temperature sensor 27b for detecting the temperature of the exhaust purification catalyst 17a is arranged on the exhaust purification catalyst 17a. Although FIG. 1 shows a configuration example in which the internal combustion engine includes the exhaust turbocharger 9 , the internal combustion engine does not have to include the exhaust turbocharger 9 . Similarly, the internal combustion engine may not have the EGR passage 18 .

The electronic control unit 30 comprises a digital computer, ROM (read only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 34, input port 35 and output port 36 connected together by a bi-directional bus 31. Equipped with The input port 35 receives output signals from the intake air amount detector 10, the pressure sensor 23, the temperature sensor 24, the air-fuel ratio sensor 25, the HC concentration sensor 26 or the CO concentration sensor 26, the temperature sensor 27b, and the NOx concentration sensor 28. It is input via the corresponding AD converter 37 . A load sensor 41 is connected to the accelerator pedal 40 to generate an output voltage proportional to the amount of depression of the accelerator pedal 40 . Furthermore, the input port 35 is connected to a crank angle sensor 42 which generates an output pulse each time the crankshaft rotates, for example, by 30°. The engine speed is calculated in the CPU 34 based on the output signal of the crank angle sensor 42 . On the other hand, the output port 36 is connected to the spark plug 3 , the fuel injection valve 4 , the throttle valve drive actuator 13 , the EGR control valve 19 and the fuel pump 21 through the corresponding drive circuit 38 . Also, the output port 36 is connected to a high-frequency power source 16d, which will be described later, a display provided in the vehicle, a speaker (not shown), and the like.

The exhaust purification catalyst 17a, which is a three-way catalyst, oxidizes HC to water and carbon dioxide, oxidizes CO to carbon dioxide, and reduces NOx to nitrogen and oxygen, respectively. Therefore, the exhaust purification catalyst 17b has noble metals such as Pt (platinum), Pd (palladium), and Rh (rhodium) as catalyst components.

FIG. 2 is a perspective view showing the configuration of the plasma generator 16. As shown in FIG. The plasma generating device 16 is a device that generates plasma by electric discharge when a voltage is applied and purifies the exhaust gas, and includes a high voltage electrode 16b and a surrounding area of the high voltage electrode 16b, through which the exhaust gas passes. It has a tube 16c and a high frequency power supply 16d. The tube 16c is grounded and functions as a ground electrode. In addition, the plasma generator 16 may be provided with a plurality of high-voltage electrodes 16b and cylinders 16c.

A high frequency voltage is applied to the high voltage electrode 16b from a high frequency power source 16d. As a result, plasma is generated between the high voltage electrode 16b and the cylinder 16c, and the exhaust gas passing through the cylinder 16c is purified. According to the plasma generation device 16, the exhaust gas is purified even before the exhaust gas purification catalyst 17b, which is a three-way catalyst, is warmed up. Therefore, the exhaust gas purification performance is improved especially when the internal combustion engine is started.

More specifically, when a high-frequency high voltage is applied between the high-voltage electrode 16b and the ground electrode (cylinder 16c), electrons are ejected from the atoms of the material forming the electrode due to discharge, and the electrons diffuse in the cylinder 16c. Then, it collides with purification target gas such as NOx flowing in the cylinder 16c. Due to the collision of electrons, the state of gas components such as NOx becomes unstable, and they are easily decomposed into N ₂ , O ₂ , etc. As a result, the exhaust gas is purified.

However, the plasma generator 16 may malfunction (failure) due to malfunctions in the high-voltage electrode 16b, the high-frequency power source 16d, the ground electrode, or the like. For example, it is assumed that the high-frequency power supply 16d does not supply power to the high-voltage electrode 16b in accordance with a command from the CPU 34, or that plasma is not generated in accordance with the amount of power supplied.

In this embodiment, a voltage higher than the voltage required to generate plasma and purify the exhaust gas is applied to the high-voltage electrode 16b, and the plasma generator 16 detects the NOx concentration in the exhaust gas at that time. is determined to be abnormal.

Here, when the voltage between the electrodes is increased when the discharge is generated, the amount of electrons ejected from the atoms increases as the discharge current increases. Also, increasing the voltage between the electrodes increases the kinetic energy of electrons ejected from the atoms.

Focusing on the relationship between the discharge voltage and the kinetic energy of electrons, the kinetic energy of electrons increases as the discharge voltage increases, and the energy at the time of collision between electrons and molecules increases. The greater the energy of the collision, the greater the effect of decomposing molecules. As a result, the variation in response increases as the voltage increases.

Equations (1) to (3) shown below show examples of variations of reactions that occur with an increase in the kinetic energy of electrons. It becomes larger in the order of formula (2) and formula (3). Specifically, the energy required for the reaction of formula (1) is about 4.2 [eV], and the energy required for the reaction of formula (2) is about 6.93 [eV]. , the energy required for the reaction of formula (3) is about 9.0 [eV].

O ₂ +e→O ⁻ +O (1)
NO+e→N+O+e (2)
_N2 +e→N+N+e (3)

For example, when the electron energy is 7 [eV], only the reactions shown in formulas (1) and (2), i.e., reactions requiring energy of 7 eV or less (decomposition of O ₂ and NOx) occurs. When O ₂ is decomposed according to equation (1), ozone is generated, and when NOx is decomposed according to equation (2), nitrogen is generated according to the following equation (4). This reduces NOx in the exhaust.

N+N→N ₂ (4)

On the other hand, when the electron energy is 9 [eV] or more, in addition to the reactions of formulas (1) and (2), the reaction of formula (3) (decomposition reaction of N ₂ ) also occurs. When _N2 is decomposed according to equation (3), the decomposed N reacts with oxygen in the air to produce NOx according to equation (5) below. Note that the reaction of formula (5) proceeds at room temperature without plasma.

N+O ₂ →NOx (5)

The susceptibility to reaction depends on the density (concentration) of molecules colliding with electrons. Since about 70 to 80% of N ₂ exists in the air, for example, when the concentration of NOx in the exhaust is less than 1%, N ₂ according to formula (3) is more likely than the decomposition reaction of NOx in formula (2). The decomposition reaction dissociating into N atoms and the subsequent reaction between the N atoms and oxygen (NOx generation reaction) of formula (5) are predominant. Therefore, increasing the discharge voltage to sufficiently increase the kinetic energy of the electrons will increase the NOx concentration in the exhaust.

In view of the above, in the present embodiment, at the time of abnormality determination, the concentration of NOx generated by increasing the voltage further than the voltage required to generate plasma and purify the exhaust gas is detected, and the NOx concentration is the threshold value. In the following cases, it is determined that the plasma generator 16 is abnormal. Specifically, if an increase in NOx can be confirmed in a state where the discharge voltage is increased to sufficiently increase the electron energy (9 eV or more), the electrode power source is operating normally, and the plasma generation device 16 generates plasma. It is determined that no abnormality has occurred in the function. On the other hand, if the increase in NOx cannot be confirmed even when the discharge voltage is increased to sufficiently increase the energy of the electrons, it is determined that the plasma generation function of the plasma generation device 16 is abnormal. be.

FIG. 3 is a schematic diagram showing functional blocks of the CPU 34 of the electronic control unit 30 for realizing the above processing. The CPU 34 is one aspect of an abnormality determination device, and includes an operating state determination unit 34a, an abnormality determination mode setting unit 34b, a voltage increase unit 34c, a NOx concentration acquisition unit 34d, an abnormality determination unit 34e, and a notification processing unit f. and have Each of these units of the CPU 34 is, for example, a functional module implemented by a computer program that runs on the CPU 34 . In other words, the functional block of the CPU 34 is composed of the CPU 34 and a program (software) for causing it to function. Moreover, the program may be recorded in the ROM 32 provided in the electronic control unit 30 or in a recording medium connected from the outside. Alternatively, each of these units included in the CPU 34 may be a dedicated arithmetic circuit provided in the CPU 34 .

An operating state determination unit 34a of the CPU 34 determines whether or not the operating state of the internal combustion engine is stable. Here, stabilizing the operating state of the internal combustion engine means that the concentration of NOx in the exhaust gas is stable. It corresponds to the case where The operating state determination unit 34a determines that the operating state of the internal combustion engine is stable, for example, when the internal combustion engine is idling, or when the internal combustion engine is in steady operation. The case where the internal combustion engine is in steady operation is, for example. This is the case when the vehicle is running steadily on a highway or the like. When the NOx concentration is stable, the detection accuracy of the NOx concentration sensor 28 is improved.

The abnormality determination mode setting unit 34b of the CPU 34 sets the operation mode of the internal combustion engine to the abnormality determination mode when the operation state of the internal combustion engine is stable and the abnormality of the plasma generator 16 is determined. When the operation mode of the internal combustion engine is set to the abnormality determination mode, the air-fuel ratio of the air-fuel mixture taken into the internal combustion engine is set to fuel-rich or stoichiometric. Further, when the operation mode of the internal combustion engine is set to the abnormality determination mode, the fuel injection from the fuel injection valve 4 is stopped and the fuel is cut.

When the air-fuel ratio of the air-fuel mixture is set to fuel-rich or stoichiometric while the operating state of the internal combustion engine is stable, the amount of NOx in the exhaust gas emitted from the engine body 1 is suppressed. In particular, when the air-fuel ratio is set to fuel-rich, almost no NOx is contained in the exhaust gas. Further, when the fuel cut is performed, the NOx concentration in the exhaust gas discharged from the engine body 1 becomes zero. Therefore, in the abnormality determination mode, the concentration of NOx generated by the increase in the discharge voltage in the plasma generator 16 can be accurately detected. In particular, when the fuel cut is performed, the concentration of NOx in the exhaust becomes 0, so the concentration of NOx generated by the increase in discharge voltage is detected with high accuracy, and the accuracy of abnormality determination is also improved. In addition, since the O ₂ concentration in the exhaust gas is high when the fuel is cut, the amount of NOx generated by the plasma increases, improving the detection accuracy of the NOx concentration.

In the case of a hybrid vehicle, even when the internal combustion engine is idling, the driving force of the motor driven by the electric power of the battery can bear the driving load. Therefore, in the case of a hybrid vehicle, the abnormality determination mode may be set during transient running.

The voltage raising unit 34c of the CPU 34 raises the voltage applied to the high-voltage electrode 16b of the plasma generator 16 to a voltage higher than the voltage for generating plasma for purifying the exhaust gas when performing abnormality determination of the plasma generator 16. Let Specifically, the voltage increasing unit 34c applies a voltage that is higher than the normal voltage at which the reactions of the above-described formulas (1) and (2) occur, when the high-frequency power supply 16d applies the voltage to the high-voltage electrode 16b. is increased to a voltage at which the reaction of equation (3) occurs. As a result, NOx is generated in the plasma generator 16 by the reactions of formulas (3) and (5).

The voltage value after the voltage increase unit 34c increases the voltage applied to the high voltage electrode 16b varies depending on the operating state of the internal combustion engine. When the internal combustion engine is idling, the amount of exhaust gas is relatively small, so the voltage value after the voltage rise is set to a relatively low value. On the other hand, when the vehicle is running steadily on a highway or the like, the amount of exhaust gas is relatively large, so the voltage value after the voltage rise is set to a relatively high value. Also, the amount of increase in voltage is greater during steady-state driving on a highway than during idling. The increased voltage value is calculated, for example, from a map that defines the relationship between the operating state of the internal combustion engine (engine speed, load (accelerator opening), cooling water temperature, etc.) and the voltage value.

Note that the voltage value before the voltage rise, that is, the voltage for generating plasma for purifying exhaust gas also differs according to the operating state of the internal combustion engine. When the load of the internal combustion engine is low, the amount of exhaust gas is relatively small, so the voltage value for generating plasma is set to a relatively low value in order to purify the exhaust gas. On the other hand, when the load of the internal combustion engine is high, the amount of exhaust gas is relatively large, so the voltage value for generating plasma is set to a relatively high value for purifying the exhaust gas. A voltage value for generating plasma for purifying exhaust gas is also calculated from a map that defines the relationship between the operating state of the internal combustion engine and the voltage value.

The NOx concentration acquisition unit 34d of the CPU 34 increases the voltage applied to the high voltage electrode 16b of the plasma generation device 16 by the voltage increase unit 34c, and determines the amount of the exhaust gas flowing through the exhaust passage downstream of the plasma generation device 16. Get the NOx concentration. Specifically, the NOx concentration acquisition section 34d acquires the NOx concentration detected by the NOx concentration sensor 28 .

The abnormality determination unit 34e of the CPU 34 determines that an abnormality has occurred in the plasma generation device 16 when the NOx concentration is equal to or less than a predetermined threshold value. Specifically, the abnormality determination unit 34e compares the NOx concentration acquired by the NOx concentration acquisition unit 34d with a predetermined threshold value, and if the NOx concentration is equal to or lower than the predetermined threshold value, an abnormality has occurred in the plasma generator 16. determine that there is On the other hand, the abnormality determination unit 34e determines that the plasma generator 16 is normal when the NOx concentration exceeds the predetermined threshold.

As described above, when the operation mode of the internal combustion engine is set to the abnormality determination mode, the NOx concentration in the exhaust gas emitted from the engine body 1 is suppressed. Therefore, when the NOx concentration in the exhaust gas flowing through the exhaust passage downstream of the plasma generator 16 detected by the NOx concentration sensor 28 exceeds a predetermined threshold value, the detected NOx is N It can be attributed to the decomposition reaction of ₂ and the subsequent reaction of formula (5). Therefore, when the NOx concentration exceeds the predetermined threshold value in the abnormality determination mode, the plasma generation device 16 is normally generating plasma, so it is determined that the plasma generation device 16 is normal. be done.

On the other hand, when the NOx concentration is equal to or less than the predetermined threshold value when the abnormality determination mode is set, the _N2 decomposition reaction of formula (3) and the subsequent reaction of formula (5) are not sufficiently performed. , it is recognized that some abnormality has occurred in plasma generation by the plasma generator 16 . Therefore, in this case, it is determined that the plasma generator 16 is abnormal.

Since the NOx generation reaction according to equations (3) and (5), that is, the NOx generation reaction by plasma, is a reaction that does not involve a catalyst, the NOx concentration detected by the NOx concentration sensor 28 is It is possible to determine the abnormality of the plasma generation device 16 based only on . Therefore, since the abnormality of the plasma generation device 16 can be determined with a simple configuration, the hardware configuration, the processing load of the CPU 34, and the circuit configuration are simplified, and the manufacturing cost related to abnormality determination is reduced.

The predetermined threshold with which the abnormality determination unit 34e compares the NOx concentration is, for example, a value determined in advance by experiments or the like. The predetermined threshold may be changed according to the operating state of the internal combustion engine. As described above, when the internal combustion engine is idling, the amount of exhaust gas is relatively small. The amount of NOx generated is relatively small. On the other hand, when the vehicle is running steadily on a highway or the like, the amount of exhaust gas is relatively large, so the amount of NOx generated when the voltage applied to the high voltage electrode 16b is increased is relatively large. . Therefore, the predetermined threshold to be compared with the NOx concentration may be higher during steady running than during idling. The predetermined threshold is calculated from a map that defines the relationship between the operating state of the internal combustion engine and the predetermined threshold.

Further, the abnormality determination unit 34e estimates the NOx amount discharged from the engine body 1 according to the operating state of the internal combustion engine, and calculates the NOx concentration corresponding to the NOx amount estimated from the NOx concentration acquired by the NOx concentration acquisition unit 34d. The current NOx concentration after subtraction may be compared with a predetermined threshold value. As a result, the NOx concentration after subtraction does not include the concentration of NOx discharged from the engine body 1, and the NOx concentration after subtraction is the concentration of NOx generated by the plasma generator 16 only. Even when NOx is discharged from the engine body 1, such as when the air-fuel ratio is set to stoichiometric in the mode, only the concentration of NOx generated by the plasma generator 16 can be obtained with high accuracy. Therefore, by comparing the post-subtraction NOx concentration with the predetermined threshold value, abnormality of the plasma generation device 16 can be determined with higher accuracy. The NOx amount discharged from the engine body 1 is calculated from a map that defines the relationship between the engine speed, operating load (accelerator opening), cooling water temperature, etc., and the NOx amount, for example.

Note that the abnormality determination unit 34e may determine that an abnormality has occurred in the plasma generation device 16 when the voltage applied to the high voltage electrode 16b cannot be increased.

The notification processing unit 34f of the CPU 34 notifies the driver of the vehicle that the plasma generation device 16 is abnormal when the abnormality determination unit 34e determines that the plasma generation device 16 is abnormal. Specifically, the notification processing unit 34f performs processing for notifying the driver that an abnormality has occurred in the plasma generation device 16 via a display or a speaker provided in the vehicle. In addition, when the vehicle is configured to be able to communicate with an external server or the like, the notification processing unit 34f may notify the driver that an abnormality has occurred in the plasma generation device 16 via e-mail, SNS, or the like. .

FIG. 4 is a flow chart showing the processing performed by the CPU 34. As shown in FIG. The processing shown in FIG. 4 is performed by the CPU 34 at predetermined control cycles. First, the operating state determination unit 34a of the CPU 34 determines whether or not the operating state of the internal combustion engine is stable (step S10). For example, when the internal combustion engine is idling, or when the internal combustion engine is in steady operation such as when the vehicle is traveling on a highway, the operating state determination unit 34a determines whether the operating state of the internal combustion engine is determined to be stable. If the operating state of the internal combustion engine is stable, the process proceeds to step S12. On the other hand, when the operating state of the internal combustion engine is not stable, the amount of NOx contained in the exhaust gas discharged from the engine body 1 is relatively large, and the accuracy of abnormality determination of the plasma generator 16 based on the NOx concentration is low. Since it becomes lower, the processing in this control cycle ends without proceeding to the subsequent processing.

When it is determined in step S10 that the operating state of the internal combustion engine is stable, the abnormality determination mode setting unit 34b of the CPU 34 sets the operation mode of the internal combustion engine to the abnormality determination mode (step S12). When the operation mode of the internal combustion engine is set to the abnormality determination mode, the air-fuel ratio of the air-fuel mixture taken into the internal combustion engine is controlled to be rich in fuel. In the abnormality determination mode, the air-fuel ratio may be set to stoichiometric, or the fuel may be cut.

Next, the voltage increasing unit 34c of the CPU 34 determines whether or not the voltage applied to the high voltage electrode 16b can be increased (step S14). Proceed to S16. In step S16, the voltage raising unit 34c raises the voltage applied to the high voltage electrode 16b to a voltage higher than the voltage for generating plasma for exhaust purification.

Next, the abnormality determination unit 34e compares the NOx concentration acquired by the NOx concentration acquisition unit 34d with a predetermined threshold value Nc, and determines whether the NOx concentration exceeds the threshold value Nc (step S18). When the NOx concentration exceeds the threshold value Nc, the abnormality determination unit 34e determines that the plasma generator 16 is normal (step S20).

On the other hand, if the NOx concentration does not exceed the threshold value Nc in step S18, the abnormality determination unit 34e determines that an abnormality has occurred in the plasma generator 16 (step S22). Next, the notification processing unit 34f of the CPU 34 notifies the driver of the vehicle that an abnormality has occurred in the plasma generator 16 (step S24). After step S24, the processing in this control cycle ends.

Further, in step S14, when the voltage applied to the high-voltage electrode 16b cannot be increased, the abnormality determination unit 34e determines that an abnormality has occurred in the plasma generation device 16 (step S22).

As described above, according to the present embodiment, the voltage applied to the high-voltage electrode 16b of the plasma generation device 16 is increased to a voltage higher than the voltage for generating plasma for exhaust purification, and the NOx concentration in the exhaust is reduced to If it is equal to or less than a predetermined threshold, it is determined that the plasma generator 16 is abnormal. Therefore, it is possible to determine the abnormality of the plasma generator 16 provided in the exhaust passage with a simple configuration.

16 plasma generator 34 CPU
34c voltage rise unit 34d NOx concentration acquisition unit 34e abnormality determination unit

Claims (1)

An abnormality determination device for determining an abnormality of a plasma generation device provided in an exhaust passage of an internal combustion engine that generates plasma by electric discharge when a voltage is applied to purify exhaust gas,
a voltage raising unit for raising the voltage applied to the plasma generation device to a voltage higher than the voltage for generating plasma for exhaust gas purification when performing abnormality determination of the plasma generation device;
a NOx concentration acquisition unit that acquires the NOx concentration in the exhaust gas flowing through the exhaust passage downstream of the plasma generation device in a state where the voltage applied to the plasma generation device is increased;
an abnormality determination unit that determines that an abnormality has occurred in the plasma generation device when the NOx concentration is equal to or lower than a predetermined threshold;
An abnormality determination device.

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